It has previously been proposed--see U.S. Pat. No. 4,174,631 (to which German Patent Disclosure Document DE-OS No. 29 38 031 corresponds) to provide temperature sensors which are essentially tubular and can be used as fever thermometers. It has been found that it is desirable that temperature sensors suitable for clinical use have a certain degree of stiffness. It has been proposed--see German Patent Disclosure Document DE-OS No. 30 49 056--to provide a ceramic cylinder, surrounded by a metal tube. Temperature sensors of this type are primarily suitable for high-temperature use, far in excess of the temperature range of a fever thermometer. The referenced German Disclosure Document, for example, discloses that the sensor has excellent mechanical stability, which can be tested, for example, by letting the sensor drop, and is suitable for temperature changes between 300.degree. C. and 600.degree. C., and has low thermal inertia and thus short response time.
For clinical use, the response time should be even shorter than that of previous temperature sensors, and should have excellent heat transfer characteristics, with low heat transfer resistance.
Low heat transfer resistance can be obtained by using a heat-conductive bridge formed of highly heat-conductive material, such as copper or silver. Use of such heat conductors has the disadvantage, however, that the heat capacity of the temperature sensor is increased. Consequently, when the temperature is used in media of low viscosity, for example when being immersed in pastes, gels, or contacted by biological tissues, in which the temperature for temperature balance is not obtained by convection--as in water--but rather by conduction to the temperature sensor, the higher heat capacity which is inherent in heat conductors to the temperature sensor necessarily increases the measuring time. The heat transfer resistance of the sensor hardly is important when contacted by the media mentioned above with respect to the heat transfer resistance in the medium itself. The measuring time, hence, is determined practically exclusively by the heat capacity of the temperature sensor itself.